Blade wheel structure for axial fan

ABSTRACT

A blade wheel structure for axial fan includes a hub and a plurality of blades circumferentially outward extended from the hub. Each of the blades has a tip portion, which is located at a windward side of the blade and is curved in shape. With the curved tip portions of the blades, it is able to create largely increased air pressure and reduce the noise produced during fan operation.

FIELD OF THE INVENTION

The present invention relates to the field of heat-dissipating fan and more particularly, to a blade wheel structure for axial fan that enables largely increased air pressure and reduced noise when the fan operates.

BACKGROUND OF THE INVENTION

Noise and low air pressure occurred during fan operation have long been two of many problems that need to be solved in the fan technical field. Currently, the problems of noise and low air pressure are generally solved by way of controlling the rotational speed via fan circuit design or changing the fan structure.

FIG. 1 shows the structure of blades 10 of a conventional fan 1. As shown, each of the blades 10 has a tip portion 11 generally in the form of a pointed or acute angle. When the fan 1 operates, air flows reaching at the tip portions 11 tend to stagnate at the generally pointed or obtuse angled position and fail to create concentrated pressure. Further, a part of the air flows directly separate from the fan blades 10 at the tip portions 11. In a worse condition, the fan blades 10 could not effectively guide the air flows to the areas at the leeward side of the blades 10 to pressurize the air flows. As a result, the conventional fan 1 has the problems of producing noise and insufficient air pressure.

It is therefore an important target for those skilled in the art to reduce the noise and increase the air pressure produced by the fan during operation thereof.

SUMMARY OF THE INVENTION

To effectively solve the problems of the conventional fan blade, it is a primary object of the present invention to provide a blade wheel structure for axial fan, which enables largely increased air pressure.

Another object of the present invention is to provide a blade wheel structure for axial fan, which largely reduces the noise produced during fan operation.

To achieve the above and other objects, the blade wheel structure for axial fan according to a preferred embodiment of the present invention includes a hub and a plurality of blades circumferentially outward extended from the hub. Each of the blades has a tip portion, which is located at a windward side of the blade and is curved in shape or formed into an obtuse angle.

In the present invention, when the fan operates, air flows will first contact with the tip portions of the blades that are located at the windward side. Since the tip portions are respectively curved in shape or formed into an obtuse angle, air flows contacting with the curved or obtuse angled tip portions will be smoothly guided to below the blades to create a pressurizing effect to obtain largely increased air pressure. In addition, the rounded or obtuse angled design for the tip portions can also create an increased surface action area at the windward side of the blades, which enables evenly pressure distribution over the tip portions to thereby reduce the noise produced during fan operation while increasing the air pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiment and the accompanying drawings, wherein

FIG. 1 is a top plan view showing a conventional fan blade structure;

FIG. 2 is a perspective view of a blade wheel structure for axial fan according to an embodiment of the present invention; and

FIG. 3 is a top plan view of the blade wheel structure for axial fan shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with a preferred embodiment thereof and by referring to the accompanying drawings.

Please refer to FIG. 2, which is a perspective view of a blade wheel structure for axial fan according to an embodiment of the present invention. For the purpose of conciseness and clarity, the present invention is also briefly referred to as the blade wheel structure and generally denoted by reference numeral 2 herein. As shown, the blade wheel structure 2 includes a hub 20 and a plurality of blades 21. The blades 21 are circumferentially outward extended from the hub 20, and respectively have a tip portion 210, which is located at a windward side of the blade 21 and is curved in shape or formed into an obtuse angle.

Please also refer to FIG. 3, which is a top plan view of the blade wheel structure 2.

More specifically, the hub 20 has a center point 200 defined in a central area thereof. A radius from the center point 200 to a circumference of the hub 20 defines a first pitch circle 3; a second pitch circle 4 concentric with the first pitch circle 3 is defined at an outer side of the first pitch circle 3 with a first radial distance D1 spaced between them; and a third pitch circle 5 concentric with the first pitch circle 3 is defined at an outer side of the first pitch circle 3 with a second radial distance D2 spaced between them. It is noted the third pitch circle 5 just passes outmost edges of the blades 21, and the first radial distance D1 is from 0.1 to 0.9 times of the radius of the first pitch circle 3. However, in the illustrated embodiment according to the present invention, there is not any particular limitation to a ratio of the first radial distance D1 to the second radial distance D2, and a user may adjust this ratio according to actual requirement in use.

Each of the tip portions 210 further includes a first arc 2100 and a second arc 2101. The first arc 2100 is extended from a point, at where the tip portion 210 meets the second pitch circle 4, to the third pitch circle 5; and the second arc 2101 is extended from another point, at where the tip portion 210 meets the first pitch circle 3, to the second pitch circle 4.

In the present invention, when the fan operates, air flows will first reach at the tip portions 210 of the blades 20 that are located at the windward side. Since the tip portions 210 are respectively curved in shape or formed into an obtuse angle, air flows contacting with the curved or obtuse angled tip portions 210 will be smoothly guided to below the blades 21 to create a pressurizing effect to obtain largely increased air flow pressure. In addition, the rounded or obtuse angled design for the tip portions 210 can also create an increased surface action area at the windward side of the blades 20, which enables evenly pressure distribution over the tip portions 210 to thereby reduce the noise produced during fan operation.

Compared to the conventional fan blade 10, the blade 21 according to the present invention has the following advantages: (1) creating largely increased air pressure; and (2) largely reducing the noise produced during fan operation.

The present invention has been described with a preferred embodiment thereof and it is understood that many changes and modifications in the described embodiment can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims. 

1: A blade wheel structure for axial fan, comprising: a hub; and a plurality of blades radially outward extended from the hub; each of the blades having a front tip portion located at a windward side of the respective blade and a rear tip portion located at one side of the blade opposite to the front tip portion, the front tip portion being curved in circular arc shape and overlapping with the rear tip portion of the adjacent blade in an axial direction; wherein each of the front tip portions further includes a first arc and a second arc, and the first arc and the second arc together define the circular arc. 2: The blade wheel structure for axial fan as claimed in claim 1, wherein the hub has a center point defined in a central area thereof; a radius from the center point to a circumference of the hub defining a first pitch circle; a second pitch circle concentric with the first pitch circle being defined at an outer side of the first pitch circle with a first radial distance spaced between the first and the second pitch circle; and a third pitch circle concentric with the first pitch circle being defined at an outer side of the first pitch circle with a second radial distance spaced between the first and the third pitch circle; the first radial distance being from 0.1 to 0.9 times of the radius of the first pitch circle; and the third pitch circle passing outmost edges of the blades. 3: The blade wheel structure for axial fan as claimed in claim 2, wherein the first arc being extended from a point, at where the tip portion meets the second pitch circle, to the third pitch circle; and the second arc being extended from another end, at where the tip portion meets the first pitch circle, to the second pitch circle. 